Realm对象添加后返回nil

当用户登录时，我创建了一个Person对象：

let creds = SyncCredentials.jwt(accessToken)
SyncUser.logIn(with: creds, server: Constants.syncAuthURL, onCompletion: { [weak self](user, err) in
if let user = user {
self?.setDefaultRealmConfiguration(with: user)
let realm = try! Realm()
let identity = (user.identity)!
let person = Person()
person.id = identity
try! realm.write {
realm.add(person, update: true)
}
self?.performSegue(withIdentifier: "showProfile", sender: self)
}                    
})

已在云服务器上成功创建人员。

在下一个视图控制器中，我喜欢基于id:获取对象

let realm = try! Realm()
guard let uuid = SyncUser.current?.identity! else { return }
let person = realm.objects(Person.self).filter("id = %@", uuid).first
try! realm.write {
person?.name = "test"
}

人总是零我也试过用主键查询对象，但没有成功。

Person类看起来像：

class Person : Object {
@objc dynamic var id = ""
@objc dynamic var created: Date = Date()
@objc dynamic var name = ""
@objc dynamic var email = ""
@objc dynamic var avatar : Data?
override static func primaryKey() -> String? {
return "id"
}
}

更新

我创建了一个新的应用程序，只有一个Viewcontroller和Person类：

class ViewController: UIViewController {
override func viewDidLoad() {
super.viewDidLoad()
let creds = SyncCredentials.usernamePassword(username: "admin", password: "test")
SyncUser.logIn(with: creds, server: Constants.AUTH_URL, onCompletion: { (user, err) in
if let user = user {
var config = user.configuration(realmURL: Constants.REALM_URL)
config.objectTypes = [Person.self]
Realm.asyncOpen(configuration: config, callback: { (realm, error) in
guard let realm = realm else {return}
let objects = realm.objects(Person.self)
print(objects) // always empty why???
try! realm.write {
let p = Person()
p.id = "test"
realm.add(p)
}
print(objects) // one object
})
}
})
}
}

和我的另一个问题一样，这个人成功地添加到了云中。但当我重新启动应用程序时，第一个查询中的对象是空的。也许我错过了对同步领域的理解？